In recent years, a variety of electronic devices are increasingly downsized, slimmed down and multifunctional, and a push switch for use in input operating sections of those electronic devices also has an increased mounting density. A push switch of a so-called horizontal push type, which is mounted at an edge section of a wiring board of an electronic device and operated by pushing in an operating section from a direction parallel to the surface of the wiring board, has also been increasingly adopted.
Such a conventional push switch is described with reference to FIGS. 12 and 13. FIG. 12 is an exploded perspective view of a conventional push switch. FIG. 13 is a side sectional view of a mounted state of the conventional push switch.
In FIGS. 12 and 13, numeral 1 denotes a case made of an insulating resin in a substantially rectangular shape seen from above, having open-top concave section 1A, and on the inner bottom surface of that concave section 1A, central fixed contact 2 and outer fixed contact 3 are electrically independently provided by insert molding. Terminals 2A, 3A respectively extended from central fixed contact 2 and outer fixed contact 3 are also fixed by insert molding, and each led outward from case 1. Further, in a position of a front bottom section of case 1, downward projection 1B projecting downward is provided.
Numeral 4 denotes an open-bottom circular dome-shaped movable contact made of an elastic metal sheet, which is housed inside concave section 1A of case 1, the peripheral lower end of which is placed on outer fixed contact 3, and the lower surface of the dome-shaped central section of which is opposed to central fixed contact 2 with a space formed therebetween. Numeral 5 denotes a protective sheet made of an insulating film and provided with an adhesive, not shown, on its lower surface, and the protective sheet is made to adhere to the upper surface position of the periphery of concave section 1A of case 1 so as to cover concave section 1A.
Numeral 6 denotes an operating body made of an insulating resin, provided with operating section 6A located in a projecting manner on the front surface side of case 1, the operating body having behind operating section 6A bar-shaped elastic projection 6B with its end formed as pushing section 6C in substantially spherical shape, and being provided with sliding section 6D in frame shape so as to surround the periphery of that elastic projection 6B. This sliding section 6D is longitudinally movably placed on protective sheet 5.
Numeral 7 denotes a cover which is made of a metal plate and controls upward movement of operating body 6, and the cover is fixed to case 1 while pushing section 6C at the end of elastic projection 6B of operating body 6 is in a contact state with the front surface of inclined surface 7A provided in the central portion.
Next described is an operation of the conventional push switch configured as above. First, when operating section 6A of operating body 6 is pushed in backward, sliding section 6D moves backward on protective sheet 5. Pushing section 6C at the end of elastic projection 6B, which is in contact with inclined surface 7A of cover 7, moves as guided diagonally downward along inclined surface 7A. The diagonally downward movement of pushing section 6C applies push-down force to movable contact 4 through protective sheet 5. When the push-down force exceeds elastic reverse force of movable contact 4, the dome-shaped portion of movable contact 4 is transformed into a bottom convex shape accompanied by a sense of click, and its lower surface comes into contact with central fixed contact 2 to which the lower surface is opposed downward, so that the switch is turned on.
When the force having pushed in operating section 6A is released, by self-restoring force of movable contact 4, movable contact 4 is restored to the original dome shape rounded upward, accompanied by a sense of click, and the above-mentioned lower surface of the central section is separated from central fixed contact 2, so that the switch is turned off. At that time, elastic projection 6B is pushed back upward by the self-restoring force of movable contact 4, and pushing section 6C at the end of elastic projection 6B moves as guided diagonally upward along inclined surface 7A of cover 7. With the movement of pushing section 6C, sliding section 6D moves forward on protective sheet 5, and operating body 6 returns to the original state.
As shown in FIG. 13, in the push switch, terminals 2A, 3A are soldered and mounted with downward projection 1B of case 1 in the state of being inserted in rectangular cut-out section 12 provided at the edge section of wiring board 11.
In this mounting state, when operating section 6A of operating body 6 is pushed in parallel to the surface of wiring board 11 for operation, downward projection 1B provided in case 1 prevents separation of the soldered portions of terminals 2A, 3A against an excessive load applied to operating body 6, by its rear surface coming to wiring board 11.
It is to be noted that as related art relevant to the invention of this application, for example, Unexamined Japanese Patent Publication Nos. 2007-329022 (Patent Document 1), 2001-210176 (Patent Document 2), and the like are known.
In response to slimming down of a variety of electronic devices, the conventional push switch has also been required to be further slimmed down while holding its mechanical strength, notably separation strength of the soldered portion.
However, the conventional push switch has a structural limit on the lowering of its height from the surface of wiring board 11. Further, although the form of Patent Document 2 is also known, this has a projection toward the lower surface of a wiring board, thus having the problem of being unable to satisfy the need for slimming down.